Connecting external antenna to 433MHZ RF kit

Projects General Guidance
1

Hello.

I am planning to use two arduino nanos to build a transmiter and receiver pair. I intend to do something similiar to "fox hunting" as it's called by the HAM radio community. Basically, I will build or buy a directional antenna, most likely a Yagi, and connect that to one arduino with an RF kit, and attempt to pick up long-range signals from another arduino nano with a simple wire antenna.
I have purchased a set of these transmitters:
ttp://www.ebay.ie/itm/130545302887?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649
Which I believe are simialir to another set offered by Seeed studio.

Upon researching Yagi antenna designs however, I realised that all of the designs I was seeing required a coaxial antenna with two mounting points, this rf kit only has one.

Based on my knowledge of antennas, I believe that the center pin of the coaxial cable carries the data, so that would connect directly to the antenna point on the rf kit. The case of the coax normally connects to ground, so, is it possible to just connect that the yagi antenna to the rf kits ground? Or is there some kind of converter I need to get to attach a coaxial cable, and therefor external antenna, to an rf kit such at this?

Thanks for any advice!

2

You are correct.
The best way to get maximum power from the transmitter is to mount a small pcb mount connector like one of these http://www.digikey.com/scripts/DkSearch/dksus.dll?v=624&lang=en&KeyWords=132357-11&WT.z_slp_buy=Amphenol-Connex_SMA-Connectors directly onto the transmitter board , and connect the antenna with a short length of 50 ohm cable .
Make sure that the antenna is designed for 433 Mhz .

3

The best way to get maximum power from the transmitter is to mount a small pcb mount connector

for me it might be typo, transmitter should use non-directional antenna, Yagi is directional, should use at receiver.

my knowledge is very rusty, last time I have a Yagi when I was kid.

4

You could write the link like this: 4KM Long Range RF link kits with encoder and decoder | eBay
Is this the seeedstudio version ?, http://www.seeedstudio.com/depot/2km-long-range-rf-link-kits-w-encoder-and-decoder-p-321.html

They have an encoder on the board, so you must use that encoder.

5

Thank you for all of your replies, I feel pretty confident about getting this to work now. I know how to design a Yagi for a particular frequency, and about impedance, etc, and physically soldering the connector shouldn't be a problem, as long as I know that center is to antenna, and case is to ground.

Erdin, yes, I'm pretty sure the seeed studio version that you posted is the same, maybe the 4KM was just a marketing thing? I am aware there is an encoder present, and I intend to use it, but would that affect the wiring of an antenna? I was under the impression that that would only affect the way in which the data is processed and transmitted?

Thanks again!

6

Yes, it only affects the way in which data is processed.

If the 4km is marketing, and 2km is also marketing. Let's assume the range is 1km. With a Yagi on the receiver side it could be a lot more, 5, 6, 7 km or more ?

7

Can a Yagi really boost the range by that much? Up to seven times? I have built (but not yet tested) a simple 4 element yagi, I assume to get the really impressive ranges you'd need 6, or even 10 element yagis? I would be happy with a decent proof of concept at this stage, anything around 2km would work for me.

8

For a self build 4 element yagi, perhaps is doubles the range with some luck.
But I'm not an expert on that, I carefully build a yagi once, and it didn't work at all!

9

JackStone:
Can a Yagi really boost the range by that much? Up to seven times? I have built (but not yet tested) a simple 4 element yagi, I assume to get the really impressive ranges you'd need 6, or even 10 element yagis? I would be happy with a decent proof of concept at this stage, anything around 2km would work for me.

I used to go fox hunting like this in the 70s. A yagi is not so good at direction finding due to the side lobes you ge. You can take readings thar are off by large angles. What we found best was to use a diaopl and use the null for the reading. The null is much sharper than the peak for most antenna.